As a transparent laminate comprising a pair of transparent substrates and an adhesive resin layer interposed between the transparent substrates, laminated glass having a pair of glass plates integrated via an adhesive layer, has been known. The laminated glass is used as windshield glass for automobiles since it has a merit that broken glass fragments are adhered to the film-form adhesive resin layer without scattering. Further, the laminated glass is also used as window glass (safety glass or security glass) for buildings since it is hard to be penetrated and is excellent in the strength. Accordingly, an adhesive resin layer of the transparent laminate is required to have good adhesion to a transparent substrate and tear resistance, in addition to excellent transparency.
As a process for producing the laminated glass, the following processes have been known.
(1) A process for producing a laminated glass by interposing an adhesive resin film between a pair of transparent substrates, followed by press-bonding the resulting laminated product under heating.
(2) A process for producing a laminated glass by injecting a liquid-form curable resin between a pair of transparent substrates the periphery of which is sealed, followed by curing the curable resin (Patent Document 1).
As compared with the process (1), the process (2) has features that cured products having various physical properties can easily be obtained depending upon purposes since a wide variety of curable resins can be used, and that a production process can be simplified by using a readily curable resin (especially, a photocurable resin).
However, the process (2) has a drawback that bubbles tends to remain in the resin at the time of injecting the curable resin.
As a method for preventing generation of the bubbles, a vacuum lamination method has been known. As a process for producing a laminated glass by means of the vacuum lamination method, for example, the following process has been known.
(3) A process for producing a laminated glass, comprising forming a layer of a photocurable resin composition on one transparent substrate and laminating the other transparent substrate on the layer of the photocurable resin composition under reduced pressure to seal the photocurable resin composition between a pair of transparent substrates, and then photocuring the photocurable resin composition under atmospheric pressure (Patent Document 2).
As a photocurable resin, a photocurable resin composition containing an unsaturated urethane oligomer has been proposed (Patent Document 1). Further, as a photocurable resin suitable for the vacuum lamination method, a photocurable resin composition containing an unsaturated urethane oligomer has been known (Patent Document 3).